#### Answer

$(x+5)^2$.

#### Work Step by Step

The given polynomial is
$=x^2+10x+25$
Write the the polynomial as $a^2+2ab+b^2$.
$=x^2+2(x)(5)+5^2$
Use perfect square trinomial pattern
$a^2-2ab+b^2=(a-b)^2$
We have $a=x$ and $b=5$.
$=(x+5)^2$
Hence, the factor of the given polynomial is $(x+5)^2$.